docs: def is_choked_turbulent_g(x, Fgamma, xT=None, xTP=None):
      r'''Calculates if a gas flow in IEC 60534 calculations is critical or
      not, for use in IEC 60534 gas valve sizing calculations.
      Either xT or xTP must be provided, depending on the calculation process.
  
      .. math::
          x \ge F_\gamma x_T
  
      .. math::
          x \ge F_\gamma x_{TP}
  
      Parameters
      ----------
      x : float
          Differential pressure over inlet pressure, [-]
      Fgamma : float
          Specific heat ratio factor [-]
      xT : float, optional
          Pressure difference ratio factor of a valve without fittings at choked
          flow [-]
      xTP : float
          Pressure difference ratio factor of a valve with fittings at choked
          flow [-]
  
      Returns
      -------
      choked : bool
          Whether or not the flow is choked [-]
  
      Examples
      --------
      Example 3, compressible flow, non-choked with attached fittings:
  
      >>> is_choked_turbulent_g(0.544, 0.929, 0.6)
      False
      >>> is_choked_turbulent_g(0.544, 0.929, xTP=0.625)
      False
  
      References
      ----------
      .. [1] IEC 60534-2-1 / ISA-75.01.01-2007
      '''
      if xT:
          return x >= Fgamma*xT
      elif xTP:
          return x >= Fgamma*xTP
      else:
          raise Exception('Either xT or xTP is needed')